This invention relates generally to methods and apparatus for biventricular pacing planning, and more particularly to methods and apparatus for enabling an eletrophysiologist, cardiologist, and/or surgeon in planning an interventional approach to take for lead placement in biventricular pacing.
It is estimated that 6-7 million people in the United States and Europe alone have congestive heart failure (CHF), the most common causes of which are ischemic and idiopathic cardiomyopathies. Prolonged PR intervals and wide QRS complexes are present in 20-50% of patients with CHF. About 29% of these patients have left bundle branch block (LBBB).
Normal electrical conduction in the heart starts in the sinoatrial node and proceeds via the atrioventricular node, His bundle, and right and left bundle branches. In patients with CHF and LBBB, long mechanical delay is present, resulting in delayed ventricular depolarization that leads to delayed left ventricular ejection. In the presence of LBBB, contraction is asymmetrical. The septum shortens first followed by stretching of the lateral wall. Subsequently, the lateral wall shortens and the septum stretches, causing ineffective contraction of the left ventricle. Cardiac resynchronization therapy, in which both the right ventricle (RV) and the left ventricle (LV) are paced simultaneously, has been shown to be effective in improving function in patients with CHF and LBBB.
Recently it has been shown that biventricular dysynchrony can also be seen in some patients with normal QRS or right bundle branch block and that biventricular pacing may be helpful in these patients. Beneficial effects of biventricular pacing have also been demonstrated in patients with atrial fibrillation.
One known method for performing biventricular pacing includes positioning the RV and right atrial lead, followed by positioning a sheath in the coronary sinus (CS). An angiogram is then performed to delineate a suitable branch for LV lead placement. The lead for LV pacing is placed in the posterior or posterolateral branch of the CS, and both RV and LV leads are then used to pace the RV and the LV simultaneously, thereby achieving synchronization with atrial contraction.
In over 20% of patients for whom biventricular pacing might otherwise be helpful, lead placement in the CS may be an unsuccessful or very lengthy procedure or the lead may dislodge from the CS. Other difficulties that can occur that may inhibit the usefulness of the procedures include unavailability of a suitable CS branch, significant rotation of the CS due to left atrial (LA) and LV dilatation, and presence of the tebesian valve. In most instances, these problems can be identified only at the time of the interventional procedure, and the procedure is either abandoned or the patient is brought back to the operating room for a second procedure where, using a surgical incision, the LV lead is placed epicardially from outside.
Some of the pitfalls involved in the use of at least one known epicardial lead placement method include having a limited view of the posterolateral or lateral area of the LV using minithoracotomy. Also, the available placement may be limited to sites that provide reasonable pacing and sensing parameters. In some cases, there may exist an inability to determine how far the LV is from the thoracic wall and/or an inability to identify the posterolateral or lateral area of the left ventricle that contracts last during the heart cycle. The methods may also run a risk of damaging the coronary arteries and venous system. In some procedures, there is an increased level of difficulty due to the presence of extrapericardial fat or no visualization of normal versus scarred tissue due to limited visibility. There may also be a difficulty in identifying the ideal position for pacing due to all of the above limitations. Furthermore, although many techniques such as tissue Doppler studies and echocardiography have been used to identify left and right ventricular asynchrony, it is not possible to identify the location that may give the most benefit from resynchronization.